Method of making quartz tubes



INVEN-TOR 5 ATTORNEY Dec. 3, 1929. A. J. LOEPSINGER METHOD OF MAKING QUARTZ TUBES Filed June 22, 1928.

, Patented Dec. 3,

UNITED STATES, PATENT OFFICE ALBERT J. LOEPSINGER, OF PROVIDENCE, RHODE ISLAND, ASSIGNOR TO GENERAL FIRE nxmmenrsnna company, or PROVIDE DELAWARE Application filed. June 22,

My invention relates to improvements in methods of making quartz tubes, and more especially has to do with a working of the tube during its formation so that the cells or voids in its wall will be disposed in everods" have been followed in making the tubes by heating from sand, in one of which the sand is fused about a graphite core to form a rough tubular slug which, while viscous, is elongated by hand in the manner familiarly practiced in making glass tubes; and in theother of which methods the sand is fused ina furnace and while still viscous is pulled directly from the furnace over a graphite mandrel of proper dimensions to form the size of tube desired. Tubes made by either method, in common with many other articles made from quartz sand, are characterized by the presence in the material of a large number of air cells or voids which prevent complete transparency and give to the material an appearance from which its trade name, opaque quartz, is derived.

The air in these cellscan not be liberated because While quartz may be brought to a viscous state it can not be made liquid enough for the air to escape by bub bling to the surface, hence the air is retained in the quartz in cells of more or less irregular shape. ,When the material is stretched or elongated to form the tubes these voids are likewise attenuated and appear in the finished tube wall as a myriad of long straight striae of exceedingly small cross-section.

These cellular striae, which may be empty or may contain air or other fluid, are elements of weakness in the finished tube and are par-, ticularly undesirable in tubes subjected to internal pressure because it has been observed that in the rupture of tubes so used, the plane of cleavagemost frequently follows one or more of these elongated voids. Since these latter extend longitudinally of the tube, in direction common with the recognized weakest dimension of the tube, they in effect constitute incipient planes of fracture and NCE, RHODE ISLAND, A CORPORATION OII' METHOD OF MAKING QUARTZ TUBES- 1928. Serial No. 287,583.

thereby materially weaken the structure. This from relied sures are employed and for such conditions it has been deemed necessary, from the standpoint of reliability tubes made from crystals.

Most of the quartz crystals available have a greater or less number of air cells or voids within them and if the finished article is to be freefroin such voids, select most carefully only those crystals which appear to have no internal imperfec: tions; Such crystals are then fused in an electric furnace in which a'vacuum is created for the purpose of withdrawing the air between the crystals, and thereby preventing the formation of any ess of adhesion. Later the crystal mass is reheated and subjected to pressure to destroy the voids and not infrequently must be reworked before the clear. These requirements add greatly to the expense ofproduction and it is only in the cases of rather expensive articles, such as may be used in laboratories or for other scientific air cells during the procfinal product is entirely and efficiency, to use only it is necessary to w purposes that such refinements of manufacture are warranted.

To follow such'practice' in the making of tubes for commercial urpo-ses would make their cost entirely pro ibitive and so, instead, after the best lookin crystals have been carefuly picked out, t in a suitable form ormold in the electric vacuum furnace and fused into a tubular slug. The resultin mass is reasonably free from voids and is own in. the trade, like other quartz articles so produced, as transparent quartz! In making a tube "from this material, the tubular slug is first secured in a. rotatable chuck and heat applied externally, the chuck and slug being rotated to insure an even distribution of the heat' and a uniform fusing of the quartz. When sufliciently viscous the free end of the slug is en aged usually by a chunk of quartz carried y another rotating chuck and the chucks separated thereby drawing out the material to form a tube.

ey are placed 7 Heretofore it has in consequence of which the quartz material,

parent quartz are much stronger.

and,

although rotating, is actually stretched along straight lines parallel to the tubes axis. Accordingly such cells or voids as were present in the quartz crystals appear in the tube wall as straight striae of small cross-section the same as in the tubes made from quartz sand. But since these voids are few in number, the commercial tubes" made of trans- Nevertheless such attenuated voids as are present are, due to their straightline arrangement, always elements of danger and constitute incipient ture not to be desired.

The resent invention is directed to the productlon of a quartz tube in which these cells or voids are not disposed in straight lines parallel to the tubes longitudinal axis but are, on the contrary, arranged in lines more or less transverse to said axis'and preferably of ever-changing direction. This is accomplished by imparting to the tube, while it is still viscous, a twisting or turning movement about its own axis. For example, when the tube is being drawn lengthwise by hand or by other means, the tube is twisted about its own axis simultaneously as it is stretched therealong. Or, if desired, the tube slug can first be fully elongated as heretofore, and the twist then imparted to the tube while it is still in the viscous state. In either event, the striae of cells orvoids are changed from their heretofore straight or linear dispositions into helically disposed linescontinuously changing in direction. In a unit length of twisted tube the cells or voids are elongated more than they would be if the same length of tube were untwisted, as a consequence of this, are also more narrowed or thinned in their cross-sectional dimension. This results in an increase of the proportion of solid material radially of the tube and a corresponding increase in strength. But the more important improvement in the tube is the distribution of the elongated cells or voids helically throughout the tube. wall, for thisalteration in the location of the cellular striae. eliminates the heretofore dangerous incipient planes of fracture runn ing lengthwise of the tube.

This new arrangement of the cellular striee so enhances the strength of the tube, especially as regards its resistlve power to internal pressure, that it makes possible the manufacture of tubes from quartz crystals as they come, without particular'selection or re'ection. Moreover, it enables twisted tulies made from quartz sand to be used under certain conditions where only tubes made from the choicest of crystals were heretofore deemed safe. In short, the invelition-not only results in tubes of greater efliciency,.but

been the practice to haveset forth lines of weakness or planes of fracenables-such tubes to be made at a considerable saving in cost.

The accompanying drawings show how the princi in ma ing a tube from a slug of transparent quartz but this showing is merely illustrative and it is to be understood that the patentable methods and features .of construction in the appended claims are also applicable in the pr duction of tubes from opaque quartz and by other processes of manipulation.

Figure 1 is an elevation showing a quartz tubular slug about to be drawn into a tube;

- Figure2 is a similar view, on smaller scale; after the drawing has taken place;

Figure 3 is an elevation of a piece of tube, prior to twisting; and

Figure 4 is a similar view, ing has taken place.

, Referring to the drawings, A represents a tubular slug of fused quartz, made either from sand or crystals, which is secured at one end to a chuck B. To the other end of this slug is presented a chunk of quartz C securedon an arbor D held in' another chuck E. 'Heat is continuously applied to slug A by the impinging flames F, the arbors and slug being rotated in order that the absorption of the heat may be uniform.

Heretofore, the rotative speed of both chucks has been the same, so that as the chucks are drawn apart and the slug elongated into a tube G, the quartz material is subjected only to straight line stretching in direction paralle to its longitudinal axis. fluid cell or void H inherent in the slug A would remain in the tube G as an attenuated space H extending in a straight direction within the wall of the tube. ings, for clearness, these cellular striee are greatly exaggerated in size.)

In the practice of the present invention, these linear cells or voids are disposed throughout the tube wall in directions constantly changing. This result is attainedby twisting the tube either while it is being drawn out, or soon after the drawing operation is completed and while'the material is still viscous. I

In Figure 2, the tube is shown fully elongated, with the cellular striae H running in straight lines longitudinally of the tube, due to the fact that while the material was being drawn out, the twochucks B and E were rotating at the same speed. By continuing the rotation (indicated by the arrow) of the lower chuck B and holding the upper chuck E still, or by rotating it at a diiferent speed, the tube is twisted orturned about its own axis thereby causing the cellular striae or attenuated voids to'be disposed helically about the tube wall, generally transverse to the longitudinal axis in ever-changing directions. If preferred, the chucks B and E after the twist- In consequence, any

(In the draw-c,

les of the-invention may be applied weakening effect of v slug of quartz along its longitudinal axis and at different relative speeds being drawn apart thus imcan be rotated while they are parting to the ously a drawing action along and a action about its own axis.

In either case the twisting, or turning of the tube about its own axis, causes the cells or voids to assume a helical illustrated in' Figure 4. This results in a further attenuation of each cell or Void as they are additionally stretched, thus increasing the proportion of the cross-section of the tube wall occupied by the quartz itself and giving the tube some additional strength. But more important than this the dislocation, or breaking up as it were, of or planes of rupture and the distribution of these lines or planes as helixes along the wall, results in a tube having markedly superior strength particularly as regards its resistive power to forces imposed upon it internally.

twisting In addition, tubes twisted as herein disclosed are more uniform in performance becausejhe greatly reduced that the presence of more or less of the helically disposed strim makes no appreciable difference. Accordingly the invention enables satisfactory tubes to; be made of ordinary crystals at much less expense than heretofore and also from quartz sand. And such tubes only tubes made from most carefully selected crystals were considered safe enough to stand the stresses imposed upon them.

'I claim as my invention:

1. The method of making a quartz tube which comprises turning. the tube about its longitudinal axis while viscous, for the u-rpose of imparting a twist in the tube wa l.

2. The method ofmaking a quartz tube which comprises elongating a viscous tubular simultaneously said axis.

3. The method of which comprises engaging the ends of a viscous tubular slug holding means adapted to twisting the material about be drawn, apart,

and imparting to said means different relation to being tive speeds of rotation whereby the tube wall is twisted about its longitudinal axis in addidrawn along said axis.

4. The method of making a quartz tube which comprises attenuating and twisting the quartz material while in the viscous state.

Signed at Providence, 21st day of June, 1928.

ALBERT J. LOEPSINGER.

tubular material simultaneconfiguration as r the straight lines the cells or voids is so can be employed where making a quartz tube by separately rotatable Rhode Island, -this 

